later in the year I'm booked on to a cl site where it seams you plug your caravan in to water supply. Question one, is an Eriba usually ok to cope with the water pressure? and sites that have this facility, do they normally drop the water pressure down ?

1. You don't have to plug in on pitch fresh water supply if you don't want to.
2. You can buy a food grade blue hose with an attachment to fit your van's water socket and that will have a pressure limiter in it. Of course the hand on the end of a wrist is a Mark One pressure limiter.
3. You can also buy a blue hose where one end screws onto the side opening on an Aquaroll and has a ballcock mechanism which limits the water level to about half fill. The water to the van is taken out through the top opening by your normal pump.
4. In both cases it's a good idea to turn off the tap if you leave the van, just in case there's an accident and the van could get flooded.

I use option 3 Ballcock mechanism with Aquaroll when on Euro fully serviced pitches as pressure would be way too much for the system without limiting.